U.S. patent number 7,215,660 [Application Number 10/435,005] was granted by the patent office on 2007-05-08 for single transceiver architecture for a wireless network.
This patent grant is currently assigned to Rearden LLC. Invention is credited to Stephen G. Perlman.
United States Patent |
7,215,660 |
Perlman |
May 8, 2007 |
Single transceiver architecture for a wireless network
Abstract
A network for wireless transmission of data includes a source
access point, a destination device and a plurality of wireless
repeaters that provide a transmission link between the source
access point and the destination device. The plurality of access
points each includes a single transceiver with separate transmitter
and receiver sections operable to simultaneously transmit and
receive data on different frequency channels. It is emphasized that
this abstract is provided to comply with the rules requiring an
abstract that will allow a searcher or other reader to quickly
ascertain the subject matter of the technical disclosure. It is
submitted with the understanding that it will not be used to
interpret or limit the scope or meaning of the claims.
Inventors: |
Perlman; Stephen G. (Palo Alto,
CA) |
Assignee: |
Rearden LLC (San Francisco,
CA)
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Family
ID: |
32853107 |
Appl.
No.: |
10/435,005 |
Filed: |
May 9, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040160928 A1 |
Aug 19, 2004 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10407445 |
Apr 4, 2003 |
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10367197 |
Feb 14, 2003 |
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Current U.S.
Class: |
370/338; 370/318;
455/3.01; 455/3.06; 455/3.05; 370/315; 455/11.1 |
Current CPC
Class: |
H04L
63/0428 (20130101); H04W 88/04 (20130101); H04B
7/15507 (20130101); H04B 7/15542 (20130101); H04W
88/08 (20130101); H04W 16/26 (20130101); H04W
76/20 (20180201) |
Current International
Class: |
H04Q
7/24 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2001111575 |
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Apr 2001 |
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JP |
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2001244864 |
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Sep 2001 |
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JP |
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PCT/US00/04840 |
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Aug 2000 |
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WO |
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Primary Examiner: D'Agosta; Steve M.
Attorney, Agent or Firm: Bereznak; Bradley J.
Parent Case Text
RELATED APPLICATIONS
This application is a continuation-in-part application of Ser. No.
10/407,445 filed Apr. 4, 2003, entitled, "SINGLE TRANSCEIVER
ARCHITECTURE FOR A WIRELESS NETWORK", which itself is a
continuation-in-part of Ser. No. 10/367,197 filed Feb. 14, 2003
entitled, "SELF-CONFIGURING, ADAPTIVE, THREE-DIMENSIONAL, WIRELESS
NETWORK".
Claims
I claim:
1. A wireless network comprising: a source device; a destination
device; and a plurality of repeaters to provide a pipelined data
transmission link between the source device and the destination
device, even numbered repeaters in the pipelined data transmission
link having a transceiver that receives on one frequency channel
and switches to another frequency channel to transmit, odd numbered
repeaters in the pipelined data transmission link having a
transceiver that receives and transmits on a single frequency
channel, each of the repeaters being located beyond an in-band
interference range, yet within a maximum bandwidth range, of
adjacent repeaters in the pipelined data transmission link.
2. The wireless network of claim 1 wherein a first repeater in the
pipelined data transmission link is located beyond the in-band
interference range, yet within the maximum bandwidth range, of the
source device.
3. The wireless network of claim 2 wherein the source device
transmits data packets on a first channel and the first repeater
receives and re-transmits the data packets on the first
channel.
4. The wireless network of claim 3 wherein the destination device
is located beyond the in-band interference range, yet within the
maximum bandwidth range, of a last repeater in the pipelined data
transmission link.
5. The wireless network of claim 4 wherein the destination device
receives the data packets on a second channel and the last repeater
receives and re-transmits the data packets on the second
channel.
6. The wireless network of claim 1 wherein the source and
destination devices operate in a 2.4 GHz frequency band.
7. The wireless network of claim 1 wherein each of the plurality of
repeaters transmits and receives in a 2.4 GHz frequency band.
8. The wireless network of claim 6 wherein a first repeater in the
pipelined data transmission link receives data packets from the
source device in the 2.4 GHz frequency band and re-transmits the
data packets in a 5 GHz frequency band, and a last repeater in the
pipelined data transmission link receives the data packets in the 5
GHz frequency band and re-transmits the data packets to the
destination device in the 2.4 GHz frequency band.
Description
FIELD OF THE INVENTION
The present invention relates generally to wireless networks, and
more particularly to methods and apparatus for configuring,
expanding and maintaining a wireless network for home or office
use.
BACKGROUND OF THE INVENTION
In recent years, wireless networks have emerged as flexible and
cost-effective alternatives to conventional wired local area
networks (LANs). At the office and in the home, people are
gravitating toward use of laptops and handheld devices that they
can carry with them while they do their jobs or move from the
living room to the bedroom. This has led industry manufacturers to
view wireless technologies as an attractive alternative to
Ethernet-type LANs for home and office consumer electronics
devices, such as laptop computers, Digital Versatile Disk ("DVD")
players, television sets, and other media devices. Furthermore,
because wireless networks obviate the need for physical wires, they
can be installed relatively easily.
Wireless communication systems adapted for use in homes and office
buildings typically include an access point coupled to an
interactive data network (e.g., Internet) through a high-speed
connection, such as a digital subscriber line (DSL) or cable modem.
The access point is usually configured to have sufficient signal
strength to transmit data to and receive data from remote terminals
or client devices located throughout the building. For example, a
portable computer in a house may include a PCMCIA card with a
wireless transceiver that allows it to receive and transmit data
via the access point. Data exchanged between wireless client
devices and access points is generally sent in packet format. Data
packets may carry information such as source address, destination
address, synchronization bits, data, error correcting codes,
etc.
A variety of wireless communication protocols for transmitting
packets of information between wireless devices and access points
have been adopted throughout the world. For example, in the United
States, IEEE specification 802.11 and the Bluetooth wireless
protocol have been widely used for industrial applications. IEEE
specification 802.11, and Industrial, Scientific, and Medical (ISM)
band networking protocols typically operate in the 2.4 GHz or 5 GHz
frequency bands. In Europe, a standard known as HIPERLAN is widely
used. The Wireless Asynchronous Transfer Mode (WATM) standard is
another protocol under development. This latter standard defines
the format of a transmission frame, within which control and data
transfer functions can take place. The format and length of
transmission frames may be fixed or dynamically variable.
Although traditional wireless networks work fairly well for
residential Internet traffic running at data rates below 1 megabit
per second (Mbps), transmission of high-bandwidth video programs is
more problematic due to the much faster video data rates.
High-bandwidth data transmissions can be degraded by the presence
of structural obstacles (e.g., walls, floors, concrete, multiple
stories, etc.), large appliances (e.g., refrigerator, oven,
furnace, etc.), human traffic, conflicting devices (e.g., wireless
phones, microwave ovens, neighboring networks, .times.10 cameras,
etc.), as well as by the physical distance between the access point
and the mobile terminal or other device. By way of example, an IEEE
802.11b compliant wireless transceiver may have a specified data
rate of 11.0 megabits per second (Mbps), but the presence of walls
in the transmission path can cause the effective data rate to drop
to about 1.0 Mbps or less. Degradation of the video signal can also
lead to repeated transmission re-tries, causing the video image to
appear choppy. These practical limitations make present-day
wireless technologies one of the most unreliable of all the
networking options available for home media networks.
One proposed solution to this problem is to increase the number of
access points in the home, with the various access points being
interconnected by a high-speed cable wire. The drawback of this
approach, however, is that it requires that cable wires be routed
through the interior of the structure.
An alternative solution is to utilize wireless repeaters to extend
coverage of the network throughout the building. For example,
D-Link Systems, Inc., of Irvine, Calif. manufactures a 2.4 GHz
wireless product that can be configured to perform either as a
wireless access point, as a point-to-point bridge with another
access point, as a point-to-multi-point wireless bridge, as a
wireless client, or as a wireless repeater. As a wireless repeater,
the product functions to re-transmit packets received from a
primary access point. But the problem with these types of wireless
repeaters is that they retransmit at the same frequency as the
primary access point device. Consequently, because the primary
access point and repeaters share the same channel, the bandwidth of
the network is effectively reduced for each repeater installed. For
example, if a data packet needs to be repeated (i.e.,
re-transmitted) three times in the same channel, each packet must
wait until the previous packet has been repeated which means that
the resulting bandwidth loss is 67%. So if the initial video
transmission starts out at, say, 21 Mbps, the effective payload
data rate at the receiver end is diminished to about 7 Mbps.
Naturally, with more repeaters, more data hops are required, so the
bandwidth loss becomes worse. This approach basically trades-off
bandwidth for signal range--extending the range of the wireless
network, but sacrificing valuable bandwidth in the process.
Still another attempted solution to the problem of wireless
transmission of video data is to lower the bandwidth of the video
through data compression. This technique involves compressing the
video data prior to transmission, then decompressing the data after
it has been received. The main drawback with
compression/decompression techniques is that they tend to
compromise the quality of the video image, which is unacceptable to
most viewers. This approach also suffers from the problem of lost
connections during transmission.
In view of the aforementioned shortcomings, there exists a strong
need for a highly reliable wireless network (e.g., on a par with
coaxial cable) that provides very high data rates (e.g., 30 Mbps)
throughout the full coverage range of a home or building.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be understood more fully from the
detailed description that follows and from the accompanying
drawings, which however, should not be taken to limit the invention
to the specific embodiments shown, but are for explanation and
understanding only.
FIG. 1 is a conceptual diagram of a wireless network according to
one embodiment of the present invention.
FIGS. 2A & 2B illustrate propagation characteristics for access
points operating in the 2.4 GHz and 5 GHz frequency bands.
FIG. 3 is an example of wireless signal repeating in accordance
with one embodiment of the present invention.
FIG. 4 is a chart illustrating pipelined data packet flow from
source to destination in accordance with one embodiment of the
present invention.
FIG. 5 is an example showing limitless data transmission range
extension in accordance with another embodiment of the present
invention.
FIG. 6 is an example of wireless signal repeating for 2.4 GHz
traffic utilizing a 5 GHz repeater backbone in accordance with
another embodiment of the present invention.
FIG. 7 is a chart illustrating pipelined data packet flow from
source to destination in accordance with the embodiment of FIG.
6.
FIG. 8 is an example of wireless signal repeating for 2.4 GHz
traffic utilizing a 5 GHz repeater backbone, with the source and
destination on the same channel in accordance with yet another
embodiment of the present invention.
FIG. 9 is a chart illustrating pipelined data packet flow from
source to destination in accordance with the embodiment of FIG.
8.
FIG. 10 is a perspective view of a wireless repeater in accordance
with one embodiment of the present invention.
FIG. 11 is a circuit block diagram of the internal architecture of
the wireless repeater shown in FIG. 10.
FIG. 12 illustrates three repeaters configured in a wireless
network according to one embodiment of the present invention.
FIG. 13 is a diagram that shows the unlimited range at full
bandwidth range of one embodiment of the present invention.
FIGS. 14A & 14B show a plan view and a side elevation view,
respectively, of a floor plan for a building installed with a
wireless network according to one embodiment of the present
invention.
FIG. 14C illustrates the repeater topology for the first floor
shown in FIGS. 14A & 14B.
FIGS. 15A & 15B show plan and side elevation views,
respectively, of the wireless network of FIGS. 14A & 14B, but
with a disturbance.
FIGS. 16A & 16B illustrate the network of FIGS. 15A and 15B
after reconfiguration to overcome the disturbance.
FIGS. 17A & 17B illustrate another example of channel conflict
in a wireless network implemented according to one embodiment of
the present invention.
FIGS. 18A & 18B illustrate the network of FIGS. 17A and 17B
after channel reconfiguration.
FIG. 19 is a floor plan showing two simultaneous wireless networks
operating in a building according to one embodiment of the present
invention.
FIG. 20 shows a wireless network according to another embodiment of
the present invention.
FIG. 21 is a circuit block diagram of the basic architecture of a
DBS tuner according to one embodiment of the present invention.
FIG. 22 is a circuit block diagram of the basic architecture of a
cable television tuner in accordance with one embodiment of the
present invention.
FIG. 23 is a circuit block diagram of the basic architecture of a
wireless receiver in accordance with one embodiment of the present
invention.
FIG. 24 is an architectural block diagram of a wireless repeater
according to another embodiment of the present invention.
FIG. 25 is an architectural block diagram of a wireless receiver in
accordance with another embodiment of the present invention.
FIGS. 26A & 26B illustrate a prior art approach to access point
transmission repeating.
FIGS. 27A & 27B show examples of access point repeating in a
network utilizing two repeaters in accordance with one embodiment
of the present invention.
FIGS. 28A & 28B show examples of access point repeating in a
network utilizing three repeaters in accordance with another
embodiment of the present invention.
FIGS. 29A 29F illustrate an exemplary transaction across a wireless
network utilizing non-access point repeaters in accordance with yet
another embodiment of the present invention.
FIGS. 30A 30F illustrate an exemplary transaction across a wireless
network utilizing access point repeaters in accordance with still
another embodiment of the present invention.
FIG. 31 is an architectural block diagram of a wireless repeater
according to yet another embodiment of the present invention.
FIG. 32A & 32B is another illustration showing propagation
characteristics for access points operating in the 2.4 GHz and 5
GHz frequency bands.
FIG. 33A is an example of wireless signal repeating in accordance
with another embodiment of the present invention.
FIG. 33B is a chart illustrating pipelined data packet flow from
source to destination in accordance with the embodiment of FIG.
33A.
FIG. 34A is an example of wireless signal repeating in accordance
with still another embodiment of the present invention.
FIG. 34B is a chart illustrating pipelined data packet flow from
source to destination in accordance with the embodiment of FIG.
34A.
FIG. 35A is an example of wireless signal repeating in accordance
with yet another embodiment of the present invention.
FIG. 35B is a chart illustrating pipelined data packet flow from
source to destination in accordance with the embodiment of FIG.
35A.
FIG. 36A is an example of wireless signal repeating in accordance
with a further embodiment of the present invention.
FIG. 36B is a chart illustrating pipelined data packet flow from
source to destination in accordance with the embodiment of FIG.
36A.
FIG. 37A is an example of wireless signal repeating in accordance
with another embodiment of the present invention.
FIG. 37B is a chart illustrating pipelined data packet flow from
source to destination in accordance with the embodiment of FIG.
37A.
DETAILED DESCRIPTION
The present invention is a wireless local area network (WLAN) that
utilizes cellular techniques to extend the range of transmission
without degrading bandwidth. The wireless network of the present
invention is thus ideally suited for transmitting video programs
(e.g., digitally-encoded video broadcast services, pay-per-view
television, on-demand video services, etc.) throughout a house or
other building, thereby creating a "media-live" environment.
In the following description numerous specific details are set
forth, such as frequencies, circuits, configurations, etc., in
order to provide a thorough understanding of the present invention.
However, persons having ordinary skill in the communication arts
will appreciate that these specific details may not be needed to
practice the present invention. It should also be understood that
the basic architecture and concepts disclosed can be extended to a
variety of different implementations and applications. Therefore,
the following description should not be considered as limiting the
scope of the invention.
With reference to FIG. 1, a wireless home media network 10
according to one embodiment of the present invention comprises a
source video access point 11 coupled to a broadband connection. By
way of example, the broadband connection may provide video content
from a Direct Broadcast Satellite (DBS) or digital cable service
provider. Additional wireless access points (simply referred to as
"access points" or "repeaters" in the context of the present
application, unless specifically described otherwise) may be
physically located in a distributed manner throughout the home or
building to provide connectivity among a variety of home media
devices configured for wireless communications. As shown in FIG. 1,
these home media devices may include a laptop personal computer 12,
DVD player 13, wireless-ready television 14, and wireless-linked
receiver 15 coupled to either a standard definition or
high-definition television (SDTV/HDTV) 16. Other types of devices,
such as personal digital assistants (PDAs), may also be coupled to
network 10 for receiving and/or transmitting data. Practitioners in
the art will appreciate that many client media devices such as
personal computers, televisions, PDAs, etc., have the capability of
detecting the operating frequency of the access point within a
particular micro-cellular transmission range.
Commands for one or more of these home media devices may be
generated using a remote control unit 17, either through infrared
(IR) or radio frequency (RF) signals. In one embodiment, wireless
network 10 provides reliable, full home coverage at throughputs
supporting multiple simultaneous video streams, e.g., two HDTV
streams at approximately 30 Mbps; eight SDTV streams at about 16
Mbps.
According to the present invention a plurality of access points is
utilized in a wireless network to provide relatively short
transmission ranges that preserve bandwidth and achieve high
reliability. The wireless network of the present invention
implements a three-dimensional ("3-D") topology in which
communications between an access point and mobile terminals or
client media devices in a particular region occur at a frequency
which is different than the communication frequency of a
neighboring region. In specific embodiments, the 2.4 GHz and 5 GHz
frequency bands are utilized for wireless transmissions. In the
United States, for instance, the 2.4 GHz band provides three
non-overlapping channels, whereas the 5 GHz band provides twelve
non-overlapping channels for simultaneous transmission traffic. The
wireless network of the present invention achieves full range
coverage in the home without bandwidth loss by utilizing a
different channel for each data packet hop. This feature allows
repeater data packets to overlap in time, as discussed in more
detail below.
FIG. 2A is a diagram illustrating the two-dimensional propagation
characteristics through open air associated with an access point 20
operating in the 2.4 GHz band and transmitting on a particular
channel, i.e., channel 1. Inner circle 21 represents the range of
maximum bandwidth, and outer circle 22 represents the range at
which the signal from access point 20 ceases to interfere with
other signals in the same channel. FIG. 2B shows an access point 30
operating in the 5 GHz band with maximum bandwidth and interference
ranges represented by circles 31 and 32, respectively. As can be
seen, both access points 20 and 30 have a relatively short range at
maximum bandwidth, but have a fairly wide interfering signal range.
Notably, access point 30 has a shorter interference range than
access point 20.
FIG. 3 is an example of wireless signal repeating in accordance
with one embodiment of the present invention. In the embodiment of
FIG. 3, each of the access points 20a 20c transmits on a different
channel. For instance, access point 20a is shown operating on
channel #1 in the 2.4 GHz band; access point 20b operates on
channel #6; and access point 20c operates on channel #11 in the
same band. The inner circles 21a 21c each denotes the ranges of
maximum bandwidth associated with access points 20a 20c,
respectively. (The outer circles 22a 22c denotes the same-channel
interference signal range associated with access points 20a 20c,
respectively.) As can be seen, each of the access points is
advantageously located at a distance within the maximum bandwidth
range of its nearest neighboring access point. Similarly, the
destination media device 25 is disposed within the maximum
bandwidth range of its nearest access point 20c.
In the example of FIG. 3, access points 20b and 20c function as
signal repeaters to facilitate transmission of data from source
access point 20a to destination device 25. To prevent loss of
bandwidth during transmission, each of the access points 20a 20c
repeats transmission of data packets on a different frequency
channel than any of its neighboring access points within signal
interference range. Access points located beyond the interference
range of a channel may reuse that same channel. In this case, a
source data packet 1 is transmitted by access point 20a on channel
#1. Access point 20b repeats transmission of this data packet on
channel #6. Access point 20c again repeats transmission of data
packet 1; this time on channel #11. Destination media device 25
receives data packet 1 from access point 20c on channel #11.
After the transmission of data packet 1, access point 20a may
immediately transmit a second source data packet ("packet 2"),
followed by a third source data packet, a fourth data packet, and
so on. Each of these data packets are repeated across the network
in a pipeline manner by access points 20b and 20c, as shown in FIG.
4. Pipelining of data packets across channels facilitates
transmission of video data without loss of bandwidth. The wireless
network of the present invention has no limitation on how far the
transmission of data can extend, as long as there are a sufficient
number of channels available.
In the 2.4 GHz band, three channels allows for three hops in any
direction (including the initial transmission from the source) in
three-dimensional space at maximum bandwidth. Since each hop
normally can extend about 50 feet at maximum bandwidth, three hops
on three different channels (one source plus two repeaters) can
cover a distance of about 150 feet from source to destination. In
the license-free 5 GHz band (e.g., 5725 MHz to 5850 MHz), there are
currently twelve channels with upwards of 54 Mbps of bandwidth
available on each channel in good transmission conditions. As with
the 2.4 GHz band, each hop in the 5 GHz band will typically extend
about 50 feet at maximum bandwidth, but the large number of
channels permits hops to extend indefinitely. That is, in a
wireless network operating in the 5 GHz band according to the
present invention, repeaters extend far enough for channel reuse.
This means that hops can extend the range of transmission from
source to destination without limitation.
FIG. 5 is an example showing a network configuration in which each
hop extends about 50 feet, so that ten hops cover about 500 feet.
In this example, after ten hops, any channel beyond its
interference range may be reused. Note that the smaller inner
circles representing the range of maximum bandwidth around the
access points that operate on the same channel frequency (e.g.,
channel #1) are separated by a considerable distance (.about.400
feet). Note that each access point is shown spaced-apart from its
nearest neighboring access point by a distance less than the
maximum bandwidth range (i.e., small circle) of its nearest
neighbor. At the same time, any two access points transmitting on
the same channel are shown separated from each by a distance
greater than the interference signal range. Access points that
re-use the same channel are separated by a distance greater than
their respective signal interference ranges. The large spatial
separation between access points using the same frequency channel
means that transmission problems due to channel interference
between access points operating on the same channel are virtually
nonexistent in the wireless network of the present invention.
In addition to neighboring access points operating on different
channels, different frequency bands may also be used during data
transmission across the wireless network of the present invention.
In an alternative embodiment, for instance, 5 GHz repeaters may be
utilized to form an arbitrary length backbone for 2.4 GHz data
traffic. This situation is illustrated in the example of FIGS. 6
& 7, which shows source access point 40a transmitting data
packets to a 2.4 GHz destination 55 using 5 GHz repeaters 40b &
40c. Note that source point 40a and repeater 40d (transmitting to
destination device 55) both operate in the 2.4 GHz band, but
utilize different channels, i.e., channels #6 and # 11,
respectively, to prevent bandwidth loss.
Another possibility is to use a 5 GHz device at the destination and
a 2.4 GHz access point at the source or vice-versa. As long as the
network is configured for communications with source-to-destination
frequency band transitions of 2.4 GHz to 5 GHz, or 5 GHz to 2.4
GHz, or 2.4 GHz to 2.4 GHz on different channels (all utilizing 5
GHz for repeaters in-between), the network can provide an arbitrary
length backbone for 2.4 gigahertz traffic, despite the fact there
are only three 2.4 GHz channels available. In other words, the
wireless network of the present invention is not limited to data
transmissions confined to a single frequency band.
It is also possible to configure a wireless network in accordance
with the present invention where the source and destination devices
both operate at 2.4 GHz using the same channel. Such an embodiment
is shown in the conceptual diagram of FIG. 8 and the associated
transmission chart of FIG. 9, wherein source access point 40a and
repeater 40d associated with destination media device 55 both
operate in the 2.4 GHz band on channel #6. Repeaters 40b and 40c
operate in the 5 GHz band on channel #1 and #2, respectively.
Although this particular embodiment has a penalty of 50% bandwidth
loss, the network still may be extended to arbitrary length with no
additional bandwidth loss, regardless of the total distance
covered. It is appreciated that the 50% bandwidth loss in this
embodiment results from the need to stagger the data packet
transmissions, as shown in the chart of FIG. 9, to avoid
interference between the packet transmission by access point 40a
and the packet transmission by repeater 40d.
With reference now to FIG. 10, there is shown a perspective view of
a wireless repeater unit 60 configured for installation in an
ordinary electrical outlet in accordance with one embodiment of the
present invention. FIG. 11 is a circuit block diagram of the
internal architecture of repeater unit 60. Repeater unit 60
comprises a transformer/power supply 61 that provides supply
voltages to the various internal electronic components, which
include a CPU 62, a RAM 63, a Flash ROM 64, and input/output
application specific integrated circuitry (I/O ASIC) 66, each of
which is shown coupled to a system bus 65. Also coupled to system
bus 65 are a plurality of transceivers, which, in this particular
embodiment, include a 5 GHz "upstream" transceiver 74, a 5 GHz
"downstream" transceiver 75, and a 2.4 GHz transceiver 76. Each of
transceivers 74 76 is coupled to an antenna 77. Additional
transceivers operating at different frequencies may be included in
repeater unit 60.
CPU 62 controls the re-transmission of the received data packets,
utilizing RAM 63 for both program execution, and for buffering of
the packets as they are received from the upstream side, i.e.,
nearest the source, before they are sent out to the downstream
side, i.e., toward the destination. Flash ROM 64 may be used to
hold software and encryption key information associated with secure
transmissions, for example, to insure that the network users are
authorized users of satellite or cable subscriber services.
In the embodiment of FIG. 11, a 1394 connector interface 70
provides a Firewire.RTM. port (coupled through a 1394 PHY physical
interface 73) to I/O ASIC 66. Also coupled to I/O ASIC 66 is a
pushbutton switch 69 and an LED indicator panel 71. Pushbutton
switch 69 may be utilized in conjunction with interface 70 to
authenticate repeater unit 60 for use in the network after the
wireless receiver or source access point has been initially
installed. These aspects of the present invention will be described
in more detail below.
By way of example, FIG. 10 further shows that the upstream repeater
in the network comprises a wireless transceiver that operates in
compliance with IEEE specification 802.11a to run with an effective
throughput of 36 Mbps utilizing large packets of approximately 2500
bytes each. Persons of skill in the art will understand that IEEE
802.11a is a standard that permits use at more than one channel at
a time. On the downstream side is another repeater that comprises a
5 GHz band, 802.11a wireless transceiver that operates on a
different frequency channel. It should be understood that the
present invention is not limited to these particular transceiver
types or frequency bands. Other embodiments may utilize other types
of transceivers; for instance, transceivers that operate in
compliance with specifications that are compatible with IEEE
specification 802.11a, 802.11b, or 802.11g, or which otherwise
provide for wireless transmissions at high-bandwidths. For the
purposes of the present application, IEEE specification 802.11a,
802.11b, 802.11g, and Industrial, Scientific, and Medical (ISM)
band networking protocols are denoted as "802.11x".
Other non-ISM bands wireless network protocols could be utilized as
well. For example, instead of utilizing 802.11a transceivers in the
5 GHz band, the network of the present invention could be
implemented using transceivers compatible with HIPERLAN2, which
runs with an effective throughput of about 42 Mbps.
Transmissions between repeater unit 60 and client wireless media
devices located nearby are shown at the top of FIG. 10. In this
example, a 36 Mbps effective throughput link is provided through an
802.11g 2.4 GHz transceiver that may be used to connect to any
local devices operating in the 2.4 GHz band. An 802.1 a compatible
transceiver may also be utilized to connect to local media devices
operating in the 5 GHz band. In a network configured with multiple
wireless repeaters, each wireless repeater may provide wireless
communications to one or more local devices. FIG. 12, for example,
illustrates three repeaters 60a 60c configured in a network wherein
each repeater may provide a communication link to nearby wireless
devices, such as laptop computers or wireless televisions, etc.
Thus, by properly distributing repeater units throughout a home or
office building, media content may be delivered at high bandwidths
to client devices located anywhere in the home or office
environment.
Repeater units 60 may be installed in the wireless network of the
present invention after the source access point (e.g., source video
receiver) has been made operational. In one embodiment, a new
repeater unit 60 is first connected to the source access point or
an existing repeater (one that is already plugged into an outlet
and coupled to the wireless network) using a Firewire cable. The
Firewire cable is connected between the existing repeater or source
access point and the new repeater. Power is provided over the
Firewire cable from the existing repeater or access point to the
new repeater to activate the internal circuitry of the new
repeater, so that encryption key information may be exchanged to
allow the new repeater to securely connect to the network.
Execution of program instructions for the exchange of encryption
information may be initiated by the person performing the
installation pressing pushbutton switch 69, located on the front
side of repeater unit 60 in FIG. 10.
After the exchange of encryption information has completed, the
Firewire cable between the two devices may be disconnected. The
repeater unit with the newly activated encryption key may then be
plugged into an electrical outlet in any location of the home or
building where the user wants the network to extend.
Once repeater unit 60 is plugged in, it immediately outputs an
indication of received signal strength on LED indicator panel 71.
LED indicator panel 71 provides an indication of transmission
signal strength to the upstream receiver, and may be advantageously
used to locate repeater unit 60 to extend the network in a home or
building. If, for example, the LED output indicates a strong
signal, the installer may wish to remove the repeater unit from its
present wall outlet location to a location farther away from the
nearest existing repeater or access point. If, upon moving to a new
location, LED indicator panel 71 outputs a "weak" or a "no signal"
reading, this means that the new repeater is too far away from
existing connection points of the network. In either case, the
installer should move the repeater unit back closer to an existing
repeater or access point until a "good" or "strong" signal strength
is indicated.
Another option is to provide an audio indication of the
transmission signal quality, instead of a visual indication.
Once the source access point (e.g., video receiver) detects the
presence a newly-activated repeater unit, it automatically
self-configures the cellular repeater wireless network. This aspect
of the present invention will be explained in greater detail
below.
The example network shown in FIG. 13 illustrates the unlimited
range at full bandwidth feature of one embodiment of the present
invention. In FIG. 13, a video access point 80 is shown running at
36 Mbps to transmit information and video data downstream to a
destination television 81 containing a wireless receiver located in
a distant room. The video data may originate from a data service
connection, such as a Direct Broadcast Satellite (DBS), DSL, or
cable television (CATV), provided to access point 80. Repeaters 60a
and 60b function as intermediary access points to distribute the
video content to client media devices in their local vicinity and
to repeat downstream data packets received on the upstream side. As
can be seen, each repeater transmits at 36 Mbps so the effective
throughput received at destination television 81 remains at 36
Mbps, i.e., without bandwidth loss.
FIGS. 14A & 14B show a plan view and a side elevation view,
respectively, of a floor plan of a building 84 installed with four
separate, secure wireless networks according to one embodiment of
the present invention. FIG. 14C illustrates the repeater topology
for the network installed on the first floor plan shown in FIGS.
14A & 14B. Source access points (e.g., video tuners or data
routers) in building 84 are denoted by circles, with the number
inside the circle designating the frequency channel used.
Additional access points (i.e., repeaters) are denoted by squares,
with the number inside the square similarly designating the channel
used for signal transmissions. In the example of FIGS. 14A 14C,
four source access points 85 88 are each shown connected to a
broadband network (e.g., cable, DSL, etc.), with each source access
points functioning as a broadband tuner/router. Thus, four separate
wireless networks are shown installed on separate floors of
building 84.
With reference to the first floor plan shown in FIGS. 14A 14C,
access point 85 transmits video data packets on channel #1 to
repeaters 91 and 92, which then both repeat the received data
packets on channel #2. Repeaters 93 and 94 (both on channel #3) are
shown branching off of repeater 91. Repeater 95 (channel #4) is
coupled to the network through repeater 93. Repeater 96 (channel
#4) branches off of repeater 94; repeater 97 (channel #1) branches
off of repeater 96; and repeater 98 (channel #2) branches off of
repeater 97 to complete the first floor topology. Note that
repeater 97 is able to reuse channel #1 since it is located a
relatively far distance from source access point 85, which uses the
same channel. Additionally, the side elevation view of FIG. 14B
shows there are no devices on the second floor network above
repeater 97 that use channel #1. For the same reasons, repeater 98
is able to reuse channel #2.
It is appreciated that access point 85 only needs one transceiver
to create the repeating wireless network shown in FIGS. 14A 14C.
The internal transceiver of access point 85 transmits on channel
#1, which transmission is then received by the upstream
transceivers of repeaters 91 and 92. Repeater 91 transmits using
its downstream transceiver on channel #2, which is then picked up
by the two upstream transceivers of repeaters 93 and 94, each of
which, in turn, transmits on their downstream transceiver to
repeaters 95 and 96, respectively, and so on. Note that in this
example, access point 98 only transmits downstream to destination
media devices, not to another access point. That is, access point
98 does not function as a repeater; rather, access point 98 simply
communicates with the destination media devices in its local
area.
Practitioners in the communications arts will also understood that
nearby access points transmitting on the same channel in the first
floor network shown in FIGS. 14A 14C (e.g., repeaters 91 & 92)
do not interfere with one another. The reason why is because a
given message or data packet is only transmitted down one path of
the topology tree at a time. Moreover, according to the embodiment
of FIGS. 14A 14C, each access point in the topology tree does not
need an arbitrary number of transceivers to repeat data messages
across the network; an upstream transceiver and a downstream
transceiver suffices. As described previously, an additional 2.4
GHz band transceiver may be included, for example, to provide
communications with 802.11b or 802.11g compatible devices. It
should be understood, however, that there is no specific limit on
the number or type of transceivers incorporated in the access
points or repeaters utilized in the wireless network of the present
invention.
Practitioners in the art will also appreciate that the tree
structure of the wireless network of the present invention is
well-suited to applications in which most of the bandwidth is
provided from a single source (e.g., a satellite or cable feed).
When the bulk of the bandwidth is from root to branch, the
repeaters disposed in the branches the tree topology can share
channels. When there is a lot of back-and-forth traffic, on the
other hand, the repeaters in the tree structure have to operate on
different channels, in case a message travels from one branch to
another branch of the tree.
The self-configuring feature of the present invention is also
apparent with reference to FIGS. 14A 14C. According to one
embodiment of the present invention, a processor in the source
access point executes a program or algorithm that determines an
optimal set of frequency channels allocated for use by each access
point or repeater. An optimal set of channels is one that does not
include over-lapping channels and avoids channels used by other
interfering devices in the same locality. An optimal channel
configuration may also be selected that maximizes channel re-use.
Further, once a set of the channels has been chosen for use by the
access points, modulated power can be reduced to the minimum needed
to achieve maximum bandwidth across each link so as to reduce
signal reflections. As discussed below, the wireless network of the
present invention may also adapt to changes to the network by
reconfiguring the channel assignments, such as when new repeaters
are added, existing ones removed, or when the network experiences
disturbances caused by other interfering devices (e.g., from a
neighboring network).
Note that in FIGS. 14A 14C, the first floor wireless network has
been configured such that the channels used by each of the access
points do not interfere with other devices located on other floors
of building 84. The side elevation view of FIG. 14B shows that
interference sources are present in the upper stories of building
84 above the wireless network created by source access point 85. To
avoid interference with the devices using channels #5 #10 on the
second through fourth floors, the first floor network has
configured itself to use channel #1, #2, #3 and #4.
The circuitry for controlling the self-configuration process may
either be centralized in the source access point or distributed
throughout the access points comprising the wireless network. In
either case, the system may proceed through a process of iteration,
wherein every possible combination of channels allocated to the
access points may be tried in order to find an optimal combination
of frequency channels. In one embodiment, the network hops through
the frequency channels automatically so that an optimal combination
of frequencies may be determined. Within a matter of seconds, the
network may complete iterating through all permutations of channels
to identify which combination of frequencies produces the best
result. One example of a best result is the highest average
bandwidth from source to each destination. Another best result may
be defined as one which optimizes bandwidth to certain destination
devices. For instance, if a particular destination device (e.g., a
video receiver) requires higher bandwidth than other destination
devices, then allocation of channels may be optimized to provide
higher bandwidth in the network path to the particular destination
device at the expense of lower bandwidth to other devices.
The system of the present invention also functions to keep
modulated power in the network to a minimum. It may be necessary in
some instances, for example when transmitting through many walls to
a maximum range, to use a lot of power. In other instances, a
repeater is located nearby and there may be few walls to transmit
through, so less transmission power is required. When the network
initially turns on, the access points may transmit at maximum power
to establish a maximum range of communication. However, once
communications have been established with all of the repeaters in
the network, the power output may be reduced to a level that
provides adequate signal transmission characteristics (i.e., a
threshold signal strength), but no more. In other words, the
network may throttle power output, keeping it only as high as it
needs to be to create a strong signal to the next repeater. One
benefit of such an operation is that it reduces signal reflections
that may interfere with the reception quality. Another benefit is
less power consumption.
Another benefit of the power management feature of the present
invention is that by having a given channel prorogate less
distance, you create the opportunity to reuse that channel in the
network at an earlier point in the topology than if transmissions
were at maximum power.
According to one embodiment, the wireless network of the present
invention automatically detects channel conflicts that arise, and
adapts the network to the conflict by reconfiguring itself to avoid
the conflict. That is, the access points monitor the signal quality
of the wireless transmissions on a continual basis. Any disturbance
or conflict that causes signal transmissions to fall below an
acceptable quality level may trigger an adaptive reconfiguration
process.
By way of example, FIGS. 15A and 15B show plan and side elevation
views, respectively, of the wireless network previously shown in
FIGS. 14A & 14B, but with a disturbance generated by the
activation of a cordless phone (shown by square 101 operating on
channel #2) in building 84. As shown, the interference caused by
cordless phone 101 is within the range of repeaters 91 and 92,
thereby affecting the transmissions of those repeaters. In
accordance with one aspect of the present invention, the network
automatically detects the channel conflict and reconfigures itself
to overcome the interference.
FIGS. 16A and 16B illustrate the network of FIGS. 15A and 15B after
reconfiguration to overcome the channel conflict caused by cordless
phone 101. As can be readily seen, building 84 is populated with
many existing channels in use. Because of the channel usage in the
upper stories, the network cannot simply swap out the channels used
by repeaters 91 & 92 with a different one. Instead, in this
example, the wireless network of the present invention replaces
channel #1 of source access point 85 with channel #5. That permits
channel #1 to replace channel #2 in both repeaters 91 & 92. In
addition, because the channel #1 usage by repeaters 91 & 92
would be too close to the channel #1 usage by repeater 97 (see
FIGS. 15A & 15B), the wireless network also replaces channel #1
of repeater 97 with channel #8. Note that channel #8 can be used
for repeater 97 because its only other use in building 84 is on the
fourth floor at the opposite end of the structure. Repeater 98 is
also shown reconfigured to use channel #1 instead of channel
#2.
The adaptation process discussed above may be performed in a
similar manner to the self-configuration process previously
described. That is, all of the different possible combinations of
channels may be tried until the network identifies an optimal
combination that works to overcome the channel conflict without
creating any new conflicts. The adaptation process may rely upon an
algorithm that does not attempt to change or move channels which
have already been established. In the example of FIGS. 16A and 16B,
for instance, channel #3, used by repeaters 93 & 94, and
channel #4, used by repeaters 95 & 96, are left in place. In
other words, regardless of the origin of a channel conflict, the
network of the present invention adapts to the disturbance by
reconfiguring itself to optimize performance.
In the unlikely event that a channel conflict is truly unavoidable,
i.e., no combination of channels exists that would allow the
network to extend from the source to any destination without
conflict (as could occur in a situation where there is heavy use of
channels by neighboring networks) the wireless network of the
present invention can reduce bandwidth and still maintain
connectivity. Such a scenario is depicted in FIGS. 17A & 17B
and FIGS. 18A & 18B.
FIGS. 17A & 17B illustrate the conflict previously shown in
FIGS. 15A & 15B, wherein a cordless phone 101 is activated,
except with an additional channel conflict created by a wireless
camera 102 operating on channel #5. Here, due to the additional
conflict caused by camera 102, there is no combination of channel
allocations that might allow the network to reach from any source
to any destination without conflict. In such a situation, the
network has adapted by reusing the same channel in consecutive
branches of the repeater topology, as shown in FIGS. 18A & 18B.
FIGS. 18A & 18B show the reconfigured wireless network with
repeaters 91 and 92 using channel #3. Because repeaters 93 and 94
also operate on channel #3 the bandwidth of the network is reduced
by 50%. The benefit of the channel switching, however, is still
preserved throughout the remainder of the network. Unlike a
conventional repeating network that continues to lose bandwidth
through each leg or repeating segment of the network, in the
special situation exemplified in FIGS. 18A & 18B there is the
only place in the network where bandwidth is lost. Moreover, the
total bandwidth loss stays at 50%; that is, bandwidth is not
continually reduced by each successive repeating segment of the
network.
In yet another embodiment of the present invention, simultaneous
wireless networks may be created to run at the same time.
Simultaneous wireless networks may be desirable in certain
applications, say, where there are three HDTV sets each operating
at 15 Mbps. If the backbone of the primary network operates at 36
Mbps, the available bandwidth is insufficient to accommodate all
three screens. The solution provided by the present invention is to
install a second video tuner (i.e., a second source access point)
and double up the number of repeaters through each branch of the
rest of the topology.
FIG. 19 is a floor plan showing two simultaneous wireless networks
operating in a building 84 to increase bandwidth. Such an
arrangement is ideally suited to support multiple HDTV video
streams. In the example of FIG. 19 access points 110 and 120 each
comprise a wireless video tuner or router with a broadband
connection. Access point 110 is shown operating on channel #1 and
access point 120 is shown operating on channel #5. In this case,
separate paths are created to the upper left and lower left
sections of the floor plan. The path from access point 110 includes
repeaters 111, 112 and 113 on respective channels #2, #3 and #4.
Meanwhile, the path from access point 120 is implemented using
repeaters 121, 122, 123, 124 and 125 on channels #6, #7, #8, #9 and
#10, respectively.
It should be understood that as long as there are a sufficient
number of channels available, bandwidth can be increased
arbitrarily in the arrangement of FIG. 19. In other words, three,
four, or more simultaneously running wireless networks may be
implemented in a home or office environment to arbitrarily increase
bandwidth to meet increasing data rate demands. If an adequate
number of channels is available (e.g., allowing extension of the
network across a sufficient distance for channel reuse), there is
no limitation on the bandwidth that can be achieved in accordance
with the present invention.
The security features provided by the wireless network of the
present invention are discussed in conjunction with the example of
FIG. 20. FIG. 20 shows a wireless network according to one
embodiment of the present invention which includes a tuner 130
coupled to receive real-time streaming media from a source, such as
DBS or CATV. Tuner 130 transmits the media content provided by the
source, possibly through one or more repeaters, to a destination
device, which in this example, comprises a wireless receiver 133,
connected to a standard definition television 134. The media
content provided by the source is, of course, encrypted. Only
authorized users or subscribers are permitted access to the media
content. Tuner 130 typically receives the media data from the cable
or satellite provider in a digitally encrypted form. This
encryption is maintained through the wireless network to SDTV 134.
Wireless receiver 133 is a trusted device; that is, it is secured
during installation by exchange of encryption key information.
Consequently, receiver 133 is able to decrypt the media content
when it arrives across the network from tuner 130. Thus, data
security is preserved across the entire span of the wireless
network, potentially over many repeater hops, so that interlopers
or unscrupulous hackers are prevented from gaining unauthorized use
of the wireless local area network.
In addition to encrypted data, the wireless network of the present
invention may also transmit presentation layer data and
information, such as overlay graphics and remote controls for
interactive experiences. To put it another way, the network may
also carry information both upstream and downstream.
Practitioners in the art will further appreciate that tuner 130 may
also digitize analog video, decode it, and compress the received
source data prior to transmission across the wireless network, in
addition to receiving compressed digital video. In the case where
compressed video is transmitted by tuner 130, receiver 133
decompresses the data as it is received. Alternatively,
decompression circuitry may be incorporated into television 134 (or
into an add-on box) that performs the same task. Receiver 133, or a
wireless-enabled television 134, may identify itself as a device
that requires high bandwidth to the upstream wireless repeaters 60
and tuner 130. When the network re-configures itself to avoid an
interference source, it may take this requirement into
consideration during channel allocation to optimize bandwidth in
the network path from tuner 130 to receiver 133 or wireless-enabled
television 134.
In an alternative embodiment, tuner 130 decrypts the real-time
media stream as it is received from the satellite or cable service
provider, and then re-encrypts that same data using a different
encryption scheme that is appropriate for the wireless local area
network. Thus, in this alternative embodiment, only devices
properly enabled by the network are authorized to play media
content received via that network. Note that because the wireless
network in this embodiment of the present invention is a single or
uni-cast signal, it can only be received by a properly enabled
receiver that is authorized with appropriate encryption key
information. In other words, the media content transmitted across
the network from source to destination is not simply available to
anyone who happens to have a receiver.
Still another possibility is for the cable or satellite company to
grant an entitlement to tuner 130 that allows a certain limited
number of streams (e.g., three or four) to be transmitted in a
particular household or office environment, regardless of the
number of media client devices that actually receive the media
content. This is simply another way to restrict distribution of the
media content.
In yet another alternate embodiment, tuner 130 receives video data
packets from a DBS or digital cable TV source and buffers the
packets in its internal RAM (see FIG. 21). The video data packets
may then be grouped together into a larger packet. For example, an
MPEG-2 transmission may have 188-byte packets, which would result
in low efficiency over a 802.11x transport. By grouping these
relatively small packets into a larger packets (e.g., twelve
188-byte packets grouped together to form a 2.256-Kbyte packet),
better 802.11x efficiency can be achieved. Many conventional
802.11x networks incur a high probability of a transmission error
when transmitting such large packets over long distances. The
occurrence of such an error, of course, requires re-transmission of
the packet, with the same risk of another error happening during
the re-transmission. By utilizing repeaters separated by relatively
short distances (i.e., within the maximum bandwidth range of the
repeaters), the transmission error rate is dramatically reduced
(e.g., <10.sup.-6) as compared to conventional wireless
networks. Thus, because larger packets (e.g., 500 bytes or greater)
may be utilized, the wireless network of the present invention is
capable of achieving a high effective throughput (e.g., as much as
36 Mbps or greater) at low error rates. By way of example, and not
limitation, one embodiment of the present invention is capable of
achieving approximately 32 Mbps effective throughput, transmitting
2.256-Kbyte packets across an 802.11x network of arbitrary length
with a bit error rate of about 10.sup.-7 or less.
Another feature of the present invention is the ability to
serendipitously provide connectivity to any user who happens to be
within the range of the wireless network. If, for instance, a
wireless repeater or access point is mounted near a window or on
the rooftop of a building, the outdoor range of the wireless
network may be extended to a nearby park or other buildings (e.g.,
a cafe or coffeehouse). A user who has a laptop computer configured
with an existing wireless transmitter and receiver, and who happens
to be within the range of the wireless network, could connect to
the Internet; view a video program; listen to an audio program; or
store media content on its disk drive for retrieval and play at a
later time (assuming proper entitlements). In other words, the
present invention provides ever greater mobility by allowing
portable computer users to take media content with them.
Media content may also be downloaded from the wireless network for
archival storage on a wireless disk server.
Those of ordinary skill in the art will further appreciate that the
wireless network of the present invention is client device
independent. It does not matter to the network what type of device
is at the destination end receiving the transmitted media content.
Video and graphics content carried on the WLAN of the present
invention can play on multiple types of television, computers
(e.g., Macintosh.RTM. or PC), different MP3 players, PDAs, digital
cameras, etc. By way of example, any PC or Mac equipped with a 2.4
GHz band wireless card can detect the presence of the wireless
network. Once it has detected the running wireless network, it may
download a driver that contains the necessary security and protocol
information for accessing the media content. Readily available
software, such as RealPlayer.RTM., QuickTime.RTM., or Windows.RTM.
MediaPlayer, may be used to play content provided through the
network.
With reference now to FIG. 21, a circuit block diagram showing the
architecture of a DBS tuner according to one embodiment of the
present invention is shown. Similar to the architecture of the
repeater unit shown in FIG. 11, a CPU 144, a RAM 145, a Flash ROM
146, and I/O ASIC 147 are coupled to a system bus 150. A 5 GHz band
downstream transceiver 156 and a 2.4 GHz band transceiver 157, both
of which are connected to antenna 160, are also coupled to system
bus 150. (An upstream transceiver is not needed at the source
end.)
Data from the satellite feed is received by a tuner 140 and output
to decryption circuitry 141, which may be configured to receive the
latest encryption key information from a smart card 142. The
decrypted digital stream output from block 141 is then re-encrypted
by encryption circuitry 143 prior to being sent over the wireless
network. As discussed above, the re-encryption is a type of
encryption appropriate for the wireless network, not one that is
locked into the satellite encryption scheme.
The architectural diagram of FIG. 21 is also shown including
connector, indicator, and pushbutton blocks 151 153, as previously
described in conjunction with FIG. 11. A power supply unit 159
provides a supply voltage to the internal electronic components of
the tuner.
FIG. 22 is a circuit block diagram illustrating the basic
architecture of a cable television tuner in accordance with one
embodiment of the present invention. Practitioners in the art will
appreciate that the architecture of FIG. 22 is somewhat more
complicated due to the presence of both analog and digital signal
channels. Elements 161 172 are basically the same as the
corresponding components of the DBS tuner described above.
Tuner 175 receives the cable feed and separates the received signal
into analog or digital channels, depending on whether the tuner is
tuned to an analog or digital cable channel. If it is an analog
channel, the video content is first decoded by block 177 and then
compressed (e.g., MPEG2 or MPEG4) by circuit block 180 prior to
downstream transmission. If it is a digital channel, a QAM
demodulator circuit 176 is used to demodulate the received signal
prior to decryption by block 178. A point of deployment (POD)
module 179, which includes the decryption keys for the commercial
cable system, is shown coupled to decryption block 178. After
decryption, the streaming media content is re-encrypted by block
181 before transmission downstream on the wireless network.
FIG. 22 shows a one-way cable system. As is well-known to persons
of ordinary skill in the art, a two-way cable system further
includes a modulator for communications back up the cable, as, for
example, when a user orders a pay-per-view movie.
FIG. 23 is a circuit block diagram illustrating the basic
architecture of a wireless receiver in accordance with one
embodiment of the present invention. Like the repeater, DBS tuner,
and cable tuner architectures described previously, the wireless
receiver shown in FIG. 23 includes a CPU 185, a RAM 186, and a
Flash ROM 187 coupled to a system bus 188. A power supply unit 184
provides a supply voltage to each of the circuit elements
shown.
A 5 GHz band upstream transceiver 189 is shown in FIG. 23 coupled
to an antenna 190 and to system bus 188. A single transceiver is
all that is required since the receiver of FIG. 23 does not
transmit downstream and it outputs directly to a display device
such as a television. As described earlier, the 5 GHz band offers
the advantage of more available channels. I/O ASIC circuitry 192
coupled to bus 188 includes the graphics, audio, decryption, and
I/O chips (commercially available from manufacturers such as
Broadcom Corporation and ATI Technologies, Inc.) needed to generate
the output signals for driving the display device. In addition to
elements 193 195 found on the repeater architecture of FIG. 11, I/O
ASIC 192 may also provide outputs to a DVI connector 196 (for
HDTV), analog audio/video (A/V) outputs 197, an SP/DIF output 198
(an optical signal for surround sound and digital audio), and an
infrared receiver port 199 for receiving commands from a remote
control unit.
FIG. 24 is a circuit block diagram of the internal architecture of
a repeater 200 according to another embodiment of the present
invention. Repeater 200 is similar to repeater unit 60 shown in
FIG. 11, except for several design changes. For instance, repeater
200 utilizes a single transceiver for upstream and downstream
transmissions rather than two transceivers, as described in the
previous embodiments. The single transceiver of repeater 200 is
separated into a 5 GHz band transmitter 214 and a 5 GHz band
receiver 215, both of which are coupled to a system bus 205. An
optional 2.4 GHz band transceiver 216, also shown coupled to a
system bus 205, may be included if the repeater is intended to
function as an access point for two-way communications with 2.4 GHz
destination devices located in the vicinity of repeater 200. In the
case where repeater 200 operates exclusively as a repeater or a 5
GHz access point, but not as a 2.4 GHz access point, transceiver
216 may be omitted.
Note that transmitter 214, receiver 215, and optional transceiver
216 are each shown connected to physically separate antennas 217a,
217b, and 217c, respectively, to provide better signal isolation.
Antennas 217 may be implemented as externally mounted wireless
antennas, or internal antennas, each having a separate physical
wire connection. Any of the previously described access points,
repeaters, tuners, etc., may also be implemented with separate
antennas for each different transceiver. Alternatively, transmitter
214, receiver 215, and optional transceiver 216 may all be
connected to a single antenna as shown in the previous
embodiments.
Transformer/power supply 201 provides supply voltages to the
various internal electronic components, which include a CPU 202, a
RAM 203, a Flash ROM 204, and input/output application specific
integrated circuitry (I/O ASIC) 2066, each of which is shown
coupled to a system bus 205. These components operate in the same
manner as described in the previous embodiments. For example, a
1394 connector interface 210 provides a Firewire.RTM. port (coupled
through a 1394 PHY physical interface 213) to I/O ASIC 206. A
pushbutton switch 209 and an LED indicator panel 211 are also
coupled to I/O ASIC 206. Switch 209 and panel 211 function in the
identical manner described in conjunction with FIG. 11. A Universal
Serial Bus (USB) connector 207 is coupled to I/O ASIC 206 to
provide an additional connection port, which may be used as an
alternative to 1394 connector interface 210.
The embodiment of FIG. 24 further comprises D.C. power connections
from supply 201 to connectors 210 and 207 for the purpose of
accommodating versions of these connectors that include power
supply pins. For example, 1394 connectors are commercially
available in 4-pin and 6-pin versions; the 6-pin version being
capable of receiving/providing power from/to its mated connector.
In the case where repeater 200 is configured with the 6-pin
connector version, it may draw power from another repeater or
source device (e.g., a digital video recorder), thereby permitting
repeater 200 to receive encryption key information to allow
repeater 200 to join the wireless network. Receiving power from a
connection to another device obviates the need to have to plug
repeater 200 into an A.C. supply line. All USB connectors such as
207 are configured with power supply pins and may be utilized in
exactly the same way. Again, the previous embodiment of FIG. 11 may
be modified to include this feature.
It is appreciated that since transmitter 214 and receiver 215 may
be located in close physical proximity to one another,
cross-channel signal interference may occur. This can be avoided by
selecting transmission frequencies that are as far apart as
possible. According to one embodiment of the present invention,
when transmitter 214 and receiver 215 operate simultaneously it is
advantageous to choose frequency channels for each that are not
adjacent to one another. For example, since there are twelve
channels currently available in the 5 GHz band, the architecture of
the present invention attempts to choose send/receive frequency
channels for transmitter 214 and receiver 215 that are as far apart
as possible (e.g., channels 1 & 12), as opposed to adjacent
channels (e.g., channels 1 & 2), to avoid signal interference.
Channel selection for transmitter 214 and receiver 215 may be
performed by CPU 202, or alternatively by another CPU (e.g., the
CPU of the source access point) in the wireless network.
The same concept of utilizing a single transceiver with transmitter
and receiver sections that can operate independently and
simultaneously may also be applied to a wireless receiver coupled
to a television or other display device. By way of example, FIG. 25
is a circuit block diagram of a wireless receiver 220 that includes
a 5 GHz band upstream transmitter 229 coupled to an antenna 230a
and to system bus 221. Since receiver 220 does not transmit
downstream (i.e., it outputs directly to a display device such as a
television) a 5 GHz band upstream receiver 228 is also included
coupled to system bus 221 and antenna 230b. Alternatively,
transmitter 229 and receiver 228 may share a single antenna, as
shown in the previous embodiment of FIG. 23.
Receiver 220 also comprises an I/O ASIC 232 coupled to bus 221. I/O
ASIC 232 includes the graphics, audio, decryption, and I/O chips
for generating the output signals used to driving the television or
display device. The elements 224 227 and 233 239 are the same as
the corresponding elements described in conjunction with the
architecture of FIG. 23. I/O ASIC 192 may also provide outputs to a
DVI connector 196 (for HDTV), analog audio/video (A/V) outputs 197,
an SP/DIF output 198 (an optical signal for surround sound and
digital audio), and an infrared receiver port 199 for receiving
commands from a remote control unit.
FIGS. 26A & 26B illustrate a prior art approach to access point
repeating in which messages are transmitted and received across a
wireless network on the same frequency channel. FIGS. 26A & 26B
show, by way of example, a source access point 240, a repeater 241,
and a destination device 242 transmitting and receiving on
frequency channel "A" for both downstream (FIG. 26A) and upstream
(FIG. 26B) transmissions. As discussed earlier, the drawback of
this approach is a loss of bandwidth. For instance, with one
repeater in the network chain there is a 50% loss of bandwidth, two
repeaters results in a 67% bandwidth loss, and so on.
FIGS. 27A & 27B respectively show downstream and upstream
transmissions in a wireless network utilizing two repeaters to
provide a transmission link between a source access point 245 and a
destination device 248 in accordance with one embodiment of the
present invention. In the network of FIGS. 27A & 27B, each of
the repeaters 246 and 247 function as access points for
communications with destination devices located in their immediate
vicinity as well as repeaters for transmissions across the network,
e.g., such as to destination device 248. Because repeaters 246 and
247 function both as access points and repeaters, their receivers
operate on a frequency channel that does not change. For example,
repeaters 246 and 247 are respectively shown operating on frequency
channels "A" and "B" for both upstream and downstream
transmissions. Maintaining a steady reception frequency channel in
repeaters 246 and 247 allows nearby devices, such as a laptop
computer, to access the network via the repeaters.
In the example diagrams of FIGS. 27A & 27B source access point
245 and destination device 248 both transmit and receive on the
same channel, i.e., channel "A" for source 245 and channel "B" for
destination 248. Repeaters 246 & 247, on the other hand, are
capable of changing their transmitting channel frequencies
according to one embodiment of the present invention in order to
minimize bandwidth loss.
As can be seen in the upstream transmission example of FIG. 27A,
source 245 transmits a message to the receiver section of repeater
246 on channel "A", and the transmitter section of repeater 246
then sends that message to the receiver portion of repeater 247 on
channel "B". Since destination device 248 is configured to receive
transmission on channel "B", repeater 247 must also transmit the
message on channel "B", with a resultant 50% loss of bandwidth due
to the fact that repeater 247 transmits and receives on the same
channel. Note, however, that this bandwidth loss is still an
improvement over the 67% bandwidth loss characteristic of the prior
art approach described above in a network with two repeaters.
For the upstream transmission example shown in FIG. 27B, repeaters
246 and 247 both change their transmitting frequencies from "B" to
"A". As was the case with the downstream transmission, the upstream
transmission incurs a 50% bandwidth loss due to the repeating of
channel "A" in both the transmitter and receiver sections of
repeater 246.
FIGS. 28A & 28B show the same concept of access point repeating
extended to three repeaters in the transmission link or network
chain, according to another embodiment of the present invention. As
was the case in FIGS. 27A & 27B, each of the repeaters 251 253
is capable of changing its transmitting frequency. The receiving
frequencies utilized by repeaters 251 253 remain steady. For
instance, the receiver portions of repeaters 251 253 are shown
configured to operate on channels "A", "B", and "C", respectively,
for both the downstream and upstream transmissions of FIGS. 28A
& 28B. Source access point 250 transmits/receives on channel
"A" and destination device 254 transmits/receives on channel "C",
regardless of the direction of transmission.
In accordance with the presently described embodiment of the
invention, each of the repeaters 251 253 changes its transmitting
frequency when switching the direction of transmission (i.e., from
upstream to downstream, or vice-versa). For example, in the
upstream transmission of FIG. 28B, the transmitter section of
repeater 251 changes from "B" to "A"; the transmitter of repeater
252 changes from "C" to "A"; and the transmitter of repeater 253
changes from "C" to "B".
In this embodiment, the upstream transmission incurs a 50%
bandwidth loss due to the repeating of channel "A" in both the
transmitter and receiver sections of repeater 251. Likewise, the
downstream transmission incurs a 50% bandwidth loss due to the
repeating of channel "C" in repeater 253. Even though each
transmission incurs a 50% bandwidth loss, this is significantly
less than the 75% bandwidth loss suffered by the prior art approach
described above with three repeaters. In other words, whereas the
prior art approach of FIGS. 26A & 26B incurs increased
bandwidth loss with additional repeaters, the single transceiver
with changing transmitter frequencies approach described in
conjunction with FIGS. 27 & 28 only results in a 50% bandwidth
loss regardless of the number of repeaters utilized in the wireless
network.
An exemplary transaction across a wireless network utilizing
non-access point repeaters that provide a transmission link between
a source and a destination device in accordance with yet another
embodiment of the present invention is shown in FIGS. 29A 29F. The
transaction illustrated comprises a request-to-send (RTS) message
sent from the source to the destination, followed by a
clear-to-send (CTS) message sent in response from the destination
back to the source. Once the CTS message is received, the source
transmits data in packet form across the network. After receipt of
the data packets, the destination issues an acknowledgement (ACK)
message for transmission across the network to the source access
point. This same basic transaction can operate in reverse; that is,
the destination can initiate a transaction by sending an RTS prior
to sending data upstream. In this latter case, the source sends CTS
and ACK messages in response at the appropriate times.
FIG. 29A shows a wireless network according to one embodiment of
the present invention in an idle state awaiting a potential RTS
issued from either source access point 256 or destination device
259. In the idle state, repeaters 257 and 258 have their receivers
set to the same frequencies that source 256 and destination 259 are
expected to transmit on. In this case, since source 256 is set to
transmit (and receive) on channel "A", the receiver of repeater 257
is also set to operate on channel "A". Similarly, because
destination device is set to transmit (and receive) on channel "C",
the receiver of repeater 258 is set to operate on channel "C". To
keep their associated transmission links active when the wireless
network is idle, repeaters 257 and 258 may periodically send simple
"ping" messages to each other (or to other neighboring repeaters in
a larger network) on the appropriate channel. In this example,
since the receiver sections of repeaters 257 and 258 are set to
channels "A" and "C", respectively, the transmitter sections of
repeaters 257 and 258 are respectively set to channels "C" and "A"
in the idle state.
It should be understood that in the particular embodiment of FIGS.
29A 29F, repeaters 257 and 258 are non-access point repeaters. That
is, repeaters 257 and 258 are intended to function solely as
repeaters in the wireless network, analogous to links in a
communication chain extending from the source to the destination.
To put it another way, repeaters 257 and 258 only serve the purpose
of carrying transmissions from source 256 to destination 259, and
vice-versa. Because repeaters 257 and 258 do not serve as access
points to intermediately located destination devices, their
receivers are not restricted to fixed frequency channels. In other
words, according to the embodiment of FIGS. 29A 29F both the
receiver and the transmitter sections of repeaters 257 & 258
may change frequency channels to maximize bandwidth of data
transmissions, as described in more detail below.
FIG. 29B illustrates the transmission of a RTS message sent from
source 256 to destination 259. The RTS message is transmitted by
source 256 on channel "A" and received by repeater 257 on the same
frequency channel. Repeater 257 then transmits the RTS message to
repeater 258 on channel "C". Since destination 259 is configured to
receive on channel "C", the transmitter section of repeater 258
changes from "A" to "C" in order to complete the transmission of
the RTS message across the wireless network. Note that a 50%
bandwidth loss occurs during the RTS transmission due to channel
"C" being utilized by both the receiver and transmitter sections of
repeater 258. Practitioners familiar with network communications,
however, will understand that because a RTS transmission is a very
brief transmission, this loss of bandwidth has virtually no affect
on the overall bandwidth of the system.
The next stage in the transaction occurs when destination device
259 sends a CTS transmission back to source 256, as shown in FIG.
29C. In this case, the transmitter sections of repeaters 257 and
258 both change from frequency channel "C" to channel "A". As was
the case with the RTS message, the CTS transmission incurs a 50%
loss of bandwidth due to the repeated use of frequency channel "A"
by repeater 257. However, because the CTS transmission is very
brief the overall bandwidth of the system is virtually
unaffected.
Once the CTS message is received by source 256, source 256 sends
the data (e.g., high bandwidth video data) to destination device
259 across the wireless network. Data transmission from source 256
to destination 259 is shown occurring in FIG. 29D. During data
transmission, both the transmitter and receiver sections of
repeaters 257 and 258 are operable to change frequencies so that
there is no effective bandwidth loss in the data transmission
between source 256 and destination device 259. In the example of
FIG. 29D, the transmitter of repeater 258 changes from frequency
channel "A" to frequency channel "C" so that destination device 259
can receive the data being sent. To prevent loss of bandwidth, the
receiver section of repeater 258 changes frequency from channel "C"
to "B". The transmitter section of repeater 257, in turn, changes
from frequency channel "A" to "B". Thus, by utilizing non-access
point repeaters with transmitter and receiver sections configured
to change frequency and operate simultaneously, the embodiment of
FIG. 29 achieves data transmission (upstream or downstream) with no
bandwidth loss.
After the last data packet is received, destination device 259
sends an acknowledgement (ACK) message back to source 256 on
channel "C", as shown in FIG. 29E. Here again, the transmitter and
receiver section of repeater 258 change frequency channels to
accommodate transmission of the ACK message. As shown in the
example of FIG. 29E, the receiver section of repeater 258 changes
to channel "C" and the transmitter section changes to channel "A".
Only the transmitter section of repeater 257 is shown changing
frequency channels (from "B" to "A") so that the repeated ACK
message can be received by source 256. As was the case with the RTS
and CTS messages, the loss of bandwidth from repeater 257
transmitting and receiving on the same channel is insignificant
since the ACK message is very brief.
Practitioners will appreciate that it is also possible to configure
the receivers of each of the repeaters to also change frequency
during the RTS, CTS, and ACK message transmissions in order to
eliminate bandwidth loss. But again, because each of these
transmissions is very brief in duration, the advantage of such
implementations is minimal.
FIG. 29F shows the wireless network returning to the idle state
once the ACK message is received by source 256. To maintain its
link with repeater 258 during the idle period, the transmitter of
repeater 257 is shown changing its operating frequency from channel
"A" to channel "C".
Another way to achieve high bandwidth operation in a wireless
network is shown in the embodiment of FIGS. 30A 30F, which
illustrates a transaction from a source access point 261 to a
destination device 264 which includes the transmission of high
bandwidth data packets, e.g., comprising high bandwidth video
signals. Destination device 264 may comprise a wireless receiver
unit, such as that shown in FIG. 25, which receives video data and
outputs a video display image to a television. In the embodiment of
FIGS. 30A 30F, destination device 264 comprises a wireless receiver
unit that includes separate transmitter and receiver sections that
operate on different frequency channels.
In the example of FIGS. 30A 30F, repeaters 262 and 263 function
both as repeaters and access points. Thus, repeaters 262 and 263
are shown with their receivers set to a fixed frequency channel. In
each of FIGS. 30A 30F, for example, the receiver of repeater 262 is
set to operate on channel "A" and the receiver of repeater 263 is
set to operate on channel "B". Nonetheless, because destination
device 264 transmits and receives on different channels the
embodiment of FIGS. 30A 30F achieves downstream data transmission
without bandwidth loss.
FIG. 30A illustrates the wireless network in an idle state much the
same as that shown in FIG. 29A. Source access point 261 is
configured to transmit and receive on frequency channel "A";
therefore, repeater 262 is set to receive a potential RTS
transmission from source 261 on channel "A". Similarly, because
destination device 264 transmits on channel "B", repeater 263 is
set to receive a potential RTS transmission from destination 264 on
channel "B". Repeaters 262 and 263 transmit on channels "B" and
"A", respectively, to maintain active transmission links in the
network.
FIG. 30B shows an exemplary RTS message sent downstream from source
261 to destination 264. In this example, the transmitter of
repeater 263 changes frequency from channel "A" to channel "C" in
order to propagate the RTS message through the network chain to
reach destination device 264. In response, destination device 264
sends back a CTS message to source 261, as shown in FIG. 30C. To
propagate the CTS message, the transmitters of repeaters 262 and
263 both change frequency to channel "A". Note that the repeated
use of channel "A" by repeater 262 results in a 50% bandwidth loss
for this very brief transmission.
Downstream data transmission is shown in FIG. 30D with no bandwidth
loss. In this case, both repeaters change their transmit
frequencies (repeater 262 changes to channel "B" and repeater 263
changes to channel "C") but maintain their receive frequencies
steady so they can function as access points as well as repeaters.
This is made possible by destination device 264 having the
capability of transmitting and receiving on different frequency
channels and each of the repeaters having their receivers set to
different channels, with only their transmitters changing
frequency.
FIG. 30E shows an ACK transmission from destination device 264 to
source 261, with repeaters 262 and 263 changing their transmit
frequencies to the same channels (both channel "A") previously used
to send the CTS message back across the network (see FIG. 30C).
FIG. 30F illustrates the network returning to an idle state
following completion of the video data transaction. To return to
the idle state following an ACK transmission, the transmitter of
repeater 262 changes frequency from channel "A" to channel "B".
Practitioners in the arts will understand that, unlike repeaters
262 and 263, the two different frequency channels of destination
device 264 are not utilized simultaneously. In other words,
destination device 264 transmits and receives at separate times.
This allows for greater cost reduction. It is further appreciated
that destination device 264 could utilize a conventional
transceiver capable of shifting its frequency (e.g., run on
frequency channel "B" during the transmission part of the
transaction, and on frequency channel "C" during the reception part
of the transaction).
It is also possible to achieve upstream transmissions according to
the present invention without bandwidth loss by modifying the
embodiment of FIG. 30 to include a source access point that
transmits and receives on different frequency channels. In still
another embodiment, as long as repeating occurs at different
frequencies in the network chain all transmission can occur in the
analog domain. In such an implementation, the carrier frequency of
the analog transmission is simply shifted by each repeater
utilizing any one of a number of well-known frequency shifting
techniques. This approach obviates the need for digital signal
conversions thereby providing certain cost benefits.
FIG. 31 is a circuit block diagram of the internal architecture of
repeater unit 270 according to still another embodiment of the
present invention. In many respects, repeater 270 is similar to
repeater of FIG. 24. For example, repeater 270 includes a
transformer/power supply 271 to provide supply voltages to the
various internal electronic components, which include a CPU 272, a
RAM 273, a Flash ROM 274, and I/O ASIC 276, each of which is shown
coupled to a system bus 275. USB and 1394 connectors 277 and 280
are configured with supply pins coupled to power supply 271 as
previously described. Repeater 270 also includes LED indicator
panel 281 and pushbutton switch 279 to assist in the installation
and connection of repeater 270 to the wireless network.
The embodiment of FIG. 31 differs from the earlier embodiments in
that it utilizes a single transceiver 285 that is capable of
operating in accordance with IEEE 802.11a, 802.11b, and the 802.11g
standards in both the 2.4 GHz and 5 GHz bands. For example, in one
implementation, transceiver 285 may comprise the AR5001X
transceiver chipset manufactured by Atheros, Inc., of Sunnyvale,
Calif. In other embodiments, transceiver 285 may comprise a single
2.4 GHz or 5 GHz band transceiver. An additional transceiver 2.4/5
GHz transceiver 286 may optionally be included in order to
configure repeater unit 270 to function as an access point as well
as a repeater. When repeater unit 270 is configured as an access
point, transceiver 286 may operate to receive requests from nearby
client devices, as well as transmit data to those devices.
As can be seen, transceiver 285 and optional transceiver 286 are
both coupled to system bus 275. Both transceivers are also shown
coupled to an antenna 287. Alternatively, transceivers 285 and 286
may each be coupled to separate antennas.
FIG. 32A is a diagram illustrating the two-dimensional propagation
characteristics through open air associated with a repeater or
access point 290 operating in the 2.4 GHz band and transmitting on
channel 1. Inner dashed circle 291 represents the in-band
interference range, which is the range where the access point or
repeater interferes with other wireless devices operating in the
same frequency band, but not necessarily on the same frequency
channel. That is, if another wireless device is located within the
in-band interference range of circle 291, then transmissions by
access point 290 (e.g., on channel 1) will interfere with the other
wireless device's ability to receive data on any channel within the
transmission frequency band. Although the in-band interference
range varies depending on such factors as transmit power, level of
isolation between channels, etc., a typical range of circle 291 is
about 2 3 feet.
The maximum bandwidth range is shown in FIG. 32A by solid circle
292. Outside of this range the signal begins to lose bandwidth due
to various impediments to signal transmission. By way of example,
2.4 GHz transceivers operating in accordance with the 802.11g
standard have a maximum bandwidth range of approximately 50 feet.
Outer dashed circle 293 represents the range at which the signal
from access point 20 ceases to interfere with other signals in the
same channel. These signal characteristics were discussed earlier
in conjunction with FIGS. 2A & 2B. FIG. 32B shows an access
point 295 operating in the 5 GHz band with in-band interference,
maximum bandwidth, and in-channel interference ranges represented
by circles 296 298, respectively. Practitioners in the art will
understand that transmissions in the 5 GHz band have somewhat
shorter in-band and in-channel interference ranges.
FIG. 33A is an example of signal repeating for a wireless network
utilizing the repeater architecture shown in FIG. 31. FIG. 33B is a
chart illustrating pipelined data packet flow from source to
destination for the example of FIG. 33A. Transmission of individual
data packets across the network is indicated by a staircase line
extending from the upper left of the diagram toward the lower
right. As can be seen, source access point 300a transmits (Tx) a
first data packet (DP.sub.1) on frequency channel 1 during cycle
time t.sub.0, which packet is then received (Rx) on channel 1 by
repeater 300b during the same cycle. Repeater 300b transmits
DP.sub.1 in cycle t.sub.1 on frequency channel 6. Repeater 300c, in
turn, receives DP.sub.1 on channel 6 and re-transmits that data
packet on channel 11 during transmission cycle t.sub.1.
In accordance with the pipelined data transmission of the present
invention, source 300a transmits DP.sub.2 in cycle t.sub.2 on
channel 1. At the same time, repeater 300c transmits DP.sub.1 on
channel 11, which is then received by destination device 305 in the
same cycle. This is made possible by the fact that each repeater is
located beyond the in-band interference range, yet within the range
of maximum bandwidth, of nearby, i.e., adjacently-located,
repeaters (as well as the source and destination devices) in the
transmission chain. For instance repeater 300b is located outside
the in-band interference range of source 300a; repeater 300c is
located outside the in-band interference range of repeater 300b;
and destination device 305 is placed outside of the in-band
interference range of repeater 300c.
Note that in the example of FIGS. 33A and 33B source device
transmits another data packet every other packet cycle, for a 50%
bandwidth loss. This bandwidth loss, however, remains the same
regardless of the number of repeaters utilized in the wireless
network. The reason why is because the network is configured such
that two repeaters (or the source device and a repeater) that
transmit simultaneously are physically located outside of each
other's in-band interference range. By way of example, in FIG. 1
source 300a and repeater 300c are located far enough away from one
another that they do not interfere.
A variation of the example of FIGS. 33A & 33B is provided in
FIGS. 34A & 34B, which shows repeater 310b (the first repeater
in the chain) reusing the same channel (e.g., channel 1) for both
receiving and transmitting; that is, repeater 310b receives
DP.sub.1 on channel 1 in cycle t.sub.0 and transmits DP.sub.1 on
channel 1 in cycle t.sub.1. The reason why repeater 310b is
permitted to transmit/receive on the same channel is because source
device 310a does not transmit during cycle t.sub.1. In this
example, repeater 310c receives DP.sub.1 on channel 1 in cycle
t.sub.1 and transmits DP.sub.1 on channel 11 to destination device
315 in cycle t.sub.2. If there were any additional repeaters in the
transmission change, they would also receive/transmit on different
channels. The implementation shown in FIGS. 34A & 34B has a
maximum bandwidth loss of 50% regardless of the number of repeaters
utilized, but advantageously reduces channel usage and switching
overhead.
The embodiment of FIGS. 35A & 35B utilizes the dual frequency
band capabilities of the single transceiver repeater architecture
shown in FIG. 31. In the configuration shown, source device 320a
and destination device 325 both operate exclusively in the 2.4 GHz
frequency band, e.g., of the 802.11b and 802.11g protocols. Source
320a, for example, transmits DP.sub.1 in the 2.4 GHz band on
channel 1 in cycle t.sub.0, which is received on the same channel
and in the same cycle by repeater 320b. Repeater 320b, however,
changes frequency bands as well as changing channels to transmit
DP.sub.1. That is to say, repeater 320b switches to the 5 GHz
frequency band (802.11a) to re-transmit DP.sub.1 on channel 5 in
cycle t.sub.1, which, in turn, is received by repeater 320c on
channel 5 in cycle t.sub.1. In cycle t.sub.3 repeater 320c changes
back to the 2.4 GHz band to transmit DP.sub.1 on channel 11 to
destination device 325.
In the embodiment of FIGS. 35A & 35B the 5 GHz band is utilized
for repeater-to-repeater signal transmission, with data
transmission between source & repeater devices and repeater
& destination devices taking place in the 2.4 GHz band. One
advantage of utilizing the 5 GHz band for repeating is that it is
basically possible to implement a wireless network with as many
repeaters as needed due to the much greater number of channels
available in the 5 GHz band. Additionally, the maximum bandwidth
loss for the wireless network of FIGS. 35A & 35B is still
limited to 50% regardless of the number of repeaters utilized in
the transmission chain.
FIGS. 36A & 36B illustrate a wireless network utilizing
repeaters according to the architecture of FIG. 31, each having a
single transceiver that operates in the 5 GHz band in a so-called
"turbo" mode in which transmissions take place on two different
channels simultaneously. Transceivers that operate in the 5 GHz
frequency band in turbo mode are commercially-available from
Atheros, Inc., of Sunnyvale, Calif. As will become apparent from
the discussion below, bandwidth loss in this embodiment is limited
to 33% no matter how many repeaters are utilized.
FIG. 36A shows a wireless network comprising a source device 330a,
repeaters 330b 330d, and destination device 335. (Note that only
the in-band interference and maximum bandwidth ranges 331 and 332,
respectively, are only shown. The in-channel interference range is
omitted to simplify the figure.) FIG. 36B shows source 330a
transmitting data packet DP.sub.1 on channel 1 in cycle t.sub.0.
Repeater 300b receives DP, on channel 1 in the 2.4 GHz band in
cycle t.sub.0. In cycle t.sub.1, repeater 300b transmits DP.sub.1
to repeater 300c in 5 GHz turbo mode utilizing channels 5 & 6
(only the lowest channel number is shown in FIGS. 36A & 36B for
clarity). Due to the fact that DP.sub.1 is simultaneously
transmitted on two different channels, the duration of cycle
t.sub.1 is only half as long as cycle t.sub.0. Repeater 330c, which
is also configured to transmit in turbo mode in this embodiment,
receives DP.sub.1 on channels 5 & 6 in the 5 GHz band in cycle
t.sub.1 and re-transmits that same data packet on channels 7 &
8 in cycle t.sub.2.
Finally, repeater 300d receives DP.sub.1 on channels 7 & 8 in
cycle t.sub.2 and then sends DP.sub.1 to destination device 325 in
the 2.4 GHz band on channel 11 in cycle t.sub.3. The transmission
of data packets DP.sub.2, DP.sub.3, and so on, continues in the
same pipelined manner described above. That is, source 330a
transmits the second data packet during cycle t.sub.2 and the first
half of cycle t.sub.3 as shown in FIG. 36B. That packet is received
by repeater 300b and re-transmitted on channels 5 & 6 in turbo
mode in the second half of cycle t.sub.2, and so on.
Practitioners in the art will appreciate that because repeaters
300b and 300c are running at twice the normal data rate, they only
need half the time normally needed to transmit in the 2.4 GHz band.
This time savings limits the bandwidth loss in the embodiment of
FIGS. 36A & 36B to 33% regardless of the number of repeaters
used in the transmission chain from source to destination. Again,
because each of the communications devices in FIGS. 36A & 36B
are located beyond each device's in-band range 331, no interference
occurs during transmissions. It should also be understood that any
of the repeaters 300b 300d could also be configured to function as
an access point through the inclusion of optional transceiver 286,
although some sort of isolation circuitry may be needed in such a
design since the two transceivers 285 and 286 might operate
simultaneously within the in-band interference range.
FIGS. 37A & 37B show another embodiment of a wireless network
according to the present invention in which every other repeater in
the transmission chain from source device 340a to destination
device 345 re-uses the same frequency channel. In other words, the
same channel is reused every second repeater. In this channel
doubling configuration repeaters 340b, 340d, and 340f all transmit
and receive data packets on the same frequency channel. Alternate
intervening repeaters 340c and 340e receive and transmit on
different channels; that is, repeaters 340c and 340e switch
channels (from Rx to Tx) during repeating.
As before, each repeater 340b 340f is located outside of the
in-band interference range 341 of other neighboring repeaters, as
well as that of the source device 340a. Destination device 345 is
also located beyond the in-band interference range 341 of repeater
340f. At the same time, each repeater (and the source and
destination devices) is located within its neighboring device's
maximum bandwidth range 342. By way of example, repeater 340b is
located within the maximum bandwidth ranges 342a & 342c, and
outside of the in-band interference ranges 341a & 341c, of
source device 340a and repeater 340c, respectively.
At any given moment, only one device in the wireless network of
FIG. 37B transmits on the same channel. Thus, the embodiment of
FIGS. 37A & 37B not only uses channels very efficiently, it
also makes it possible to extend the wireless network of the
present invention over a greater distance. In other words, given
the limited number of available channels in a frequency band (e.g.,
the 2.4 GHz band only has three available channels) the wireless
network of FIGS. 37A & 37B can extend a farther distance than
the previous embodiments that do not employ channel doubling from
source to destination. Additionally, in the wireless network of
FIG. 37B the bandwidth loss is limited to 50% regardless of the
number of repeaters utilized in the transmission chain. In the
event that there is a delay for transceivers to switch channels,
the channel doubling embodiment of FIG. 37B also reduces
channel-switching latency by 50% as compared to channel switching
on every repeater.
It should be understood that elements of the present invention may
also be provided as a computer program product which may include a
machine-readable medium having stored thereon instructions which
may be used to program a computer (or other electronic device) to
perform a process. The machine-readable medium may include, but is
not limited to, floppy diskettes, optical disks, CD-ROMs, and
magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, magnet or
optical cards, propagation media or other type of
media/machine-readable medium suitable for storing electronic
instructions. For example, elements of the present invention may be
downloaded as a computer program product, wherein the program may
be transferred from a remote computer (e.g., a server) to a
requesting computer (e.g., a client) by way of data signals
embodied in a carrier wave or other propagation medium via a
communication link (e.g., a modern or network connection).
Additionally, although the present invention has been described in
conjunction with specific embodiments, numerous modifications and
alterations are well within the scope of the present invention.
Accordingly, the specification and drawings are to be regarded in
an illustrative rather than a restrictive sense.
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